The present invention relates to systems and methods for investigating ion transport through cellular membranes, and in particular to systems and methods that may provide rapid measurement of ion channel activity.
The lipid bilayers that make up cell membranes include ion channels that control the flow of ions into and out of cells. Certain ion channels open in response to signaling molecules including naturally occurring signaling molecules and drug molecules. In the development of therapeutic drugs it is necessary to determine the effect of the drug on ion channels either to avoid adverse effects or to create a positive therapeutic effect for the treatment of ion-channel related diseases.
Analysis of the response of ion channels may be conducted with a so-called “patch-clamp,” traditionally a micropipette adhered to the surface of a cell by a slight suction. An electrical connection across the membrane of the cell is then made by one of a number of techniques, for example, by applying a sharp suction pulse to the pipette to open a hole in the cell wall. Measurement of small electrical changes across the cell membrane made by a miniature electrode inserted into or near the opening may then be used to deduce the flow of ions through the ion channels. The small amounts of electrical current involved in these measurements require an extremely high resistance seal between the pipette and the cell wall (a Giga-ohm seal).
Drug screening often requires making many ion-channel measurements. Accordingly the pipette having a single opening has been replaced with a plate having multiple small pores each of which may accept a cell. The plate array allows the parallel processing of multiple cells and may be more readily integrated into automated equipment.
The sensitivity of measurements of small current flows through ion channels can be significantly limited by the poor electrical characteristics of a bare electrode immersed in the aqueous medium inside or outside of the cell. As a result, rapid changes in ionic transport may be difficult to resolve. It is desirable to understand and resolve such changes, for example, in the context of medications that may affect the human body.
Improvements in such systems, including as described in U.S. Pat. No. 8,217,665, which is hereby incorporated by reference, provide a patch-clamp system employing high-frequency characterization of cell wall membranes. Changes in the frequency response of a tank circuit incorporating the cell wall membrane impedance provides highly sensitive and highly time-resolved measurements of ion channel activity. However, the above systems are typically limited by their data acquisition speeds and resolutions.